JPH0766201B2 - Electrophotographic developer composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a developer composition for developing an electrostatic charge image in electrophotography, electrostatic recording, electrostatic printing, and the like, and more specifically, to a positive charging property. The present invention relates to a developer composition.

[Conventional technology and problems]

Conventional electrophotographic methods include U.S. Pat.
No. 7809, the photoconductive insulating layer is uniformly charged, and then the layer is exposed to light to dissipate the charge on the exposed portion to form an electrical latent image. After being formed and further visualized by adhering fine powder having a colored charge called toner to the latent image (developing step), the obtained visible image is transferred to a transfer material such as transfer paper. (Transfer process), Permanent fixing by heating, pressure, or other suitable fixing method (fixing process)
Consists of steps.

In this way, toner is not only used in the development process, but also in the transfer process,
It must have the functions required in each step of the fixing process.

Recently, as electrophotographic photoconductors for copying machines, printers, etc., those using organic photoconductors in addition to the conventional inorganic type (amorphous selenium alloy, cadmium sulfide, etc.) have been increasing. ing. This is due to the ease of manufacturing the organic photoconductor, the low cost, the harmlessness, and the like.

Most organic photoconductors require a toner having a positive chargeability due to their properties, and the increase in laser beam printers that perform reversal development even if inorganic photoconductors are used. Therefore, development of high-performance positively charged toner has been earnestly desired.

Conventionally, as a toner of this type, a vinyl resin or an epoxy resin represented by a styrene-acrylic copolymer, which is almost neutral in charge, is used as a binder, and a colorant, a charge control agent, etc. are added to the toner particles. The above products have been used for reasons such as ease of manufacturing. Due to the properties of the resin used, the toner using these resins as binders satisfies all of the important required properties such as offset resistance, blocking resistance, low temperature fixing property, vinyl chloride migration resistance, etc. There is nothing to do.

That is, in the case of a vinyl-based resin represented by styrene-acrylic copolymer, if the offset resistance is to be improved,
There is no choice but to raise the softening point and crosslink density of the resin, and the low temperature fixability is sacrificed. On the contrary, if low temperature fixability is pursued, offset resistance and blocking resistance will be impaired. Also, since the solubility parameter of the styrene-acrylic copolymer is close to the solubility parameter of the plasticizer (dioctyl phthalate etc.) contained in vinyl chloride etc.,
The transfer of the plasticizer to the toner side occurs, which is a cause of contamination of copy images stored on a vinyl chloride sheet or the like.

When an epoxy resin is used, it has vinyl chloride migration resistance, but it is very difficult to improve offset resistance and low-temperature fixability by itself, and it cannot be used especially by an apparatus using a heat roll type fixing device.

Although attempts have been made to improve these drawbacks, they have not been fundamentally resolved.

On the other hand, polyester is attracting attention as a binder resin having a wide molecular weight distribution and satisfying the required properties such as offset resistance, low temperature fixing property, blocking resistance, and vinyl chloride migration resistance in a well-balanced manner. Here, the relationship between the chargeability of polyester and its acid value is almost proportional, and it is known that the higher the acid value, the greater the negative chargeability of the resin. The polyesters described in JP-A-57-37353 and JP-A-57-109825 have a crosslinked structure,
Since it has a relatively high acid value, it is an excellent binder resin having sufficient negative chargeability without using a charge control agent.

However, if these cross-linking type polyesters are used for a binder resin for a toner having a positive chargeability, a large amount is required to give a positive chargeability due to the negative chargeability of the resin itself. Therefore, it is necessary to take measures such as having to mix the positive charge control agent of Generally, nigrosine dye is known as a positive charge control agent, but when used in a large amount, the compatibility with the binder resin that constitutes the main component of the toner is poor, and the toner particles are mixed for a long time in the developing device. Then, particles are destroyed, and when nigrosine or the like is simply dispersed, particles of reverse (negative) polarity that do not contain nigrosine or the like are generated, and so-called background fog in which toner adheres even where there is no image signal. The phenomenon occurs. In addition, when a large amount of nigrosine dye or the like is used, since it has hydrophilicity, the amount of charge changes depending on the environmental humidity, and the image quality deteriorates. Nigrosine-based dyes generally have strong coloring and are not compatible with color toners.

On the other hand, as the versatility of the copying machine increases, it is often installed under severe conditions, for example, high temperature and high humidity or low temperature and low humidity, and even under such severe conditions, the normal environment is maintained. It is indispensable to obtain a clear image similar to.

However, although the toner has preferable electrical properties such as a preferable charge amount and insulation resistance under normal conditions, they largely fluctuate under high temperature and high humidity or low temperature and low humidity, resulting in image deterioration. There are many things. For example, the image density is reduced under low temperature and low humidity, and is increased under high temperature and high humidity. In the polyester having hydrophilic carboxyl group and hydroxyl group at the polymer terminal, if the concentration thereof, that is, the acid value or the hydroxyl value is too high, it may be susceptible to the above environment.

Therefore, there is a demand for a toner capable of obtaining a clear image that is completely the same as the normal environmental conditions under any environment.

[Object of the Invention]

The present invention has been made under the background as described above, and its object is to provide a clear and fog-free image in a developer for electrophotography by using a toner binder resin having a charge property close to neutrality. More specifically, the present invention is to provide a toner having a positive chargeability which is excellent in durability and which has an extremely small influence of environmental humidity and which has improved the above-mentioned drawbacks.

Another object of the present invention is to provide a developer capable of preventing offset in a heat roller fixing system without applying an offset preventing liquid and fixing at a lower fixing temperature.

It is another object of the present invention to provide a phenomenon agent in a heat roller fixing method, in which offset can be prevented without adding an offset inhibitor and fixing can be performed at a lower fixing temperature.

Another object of the present invention is to provide a developer which can be fixed in a shorter time and with lower energy in a flash fixing method or an oven fixing method.

Another object of the present invention is to provide a developer which has good fluidity, does not cause blocking, and has a long life (hard deterioration).

Another object of the present invention is to provide a developer having good kneadability and pulverizability during production of the developer.

Another object of the present invention is to provide a developer in which an image is not contaminated even when it comes into contact with a sheet or file such as vinyl chloride.

[Means for solving problems]

The present inventors have arrived at the present invention as a result of earnest research in order to achieve the above object.

That is, the present invention is a developer composition for electrophotography, which comprises a thermoplastic resin as an essential component, wherein the thermoplastic resin has at least one trifunctional or higher polyfunctional compound as a constituent unit.
The present invention relates to a developer composition for electrophotography, which is a polyester having an acid value of 5 KOHmg / g or less and a hydroxyl value of 60 KOHmg / g or less and containing a positive charge control agent.

Among the monomers constituting the polyester in the present invention, examples of alcohol monomers include polyfunctional monomers having a valence of 3 or more, such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol and 1,3-propylene. Diols such as glycol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, bisphenol A, hydrogenated bisphenol A, polyoxyethylenated Bisphenol A alkylene oxide adducts such as bisphenol A and polyoxypropyleneized bisphenol A, other dihydric alcohols, or sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, and diether Pentaerythritol, Tripe Intaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, tri Methylolpropane,
Mention may be made of 1,3,5-trihydroxybenzene and other trihydric or higher polyhydric alcohols.

Among these monomers, the system using the bisphenol A alkylene oxide adduct as the main component monomer showed good results.

When a bisphenol A alkylene oxide adduct is used as a constituent monomer, a polyester having a relatively high glass transition point is obtained due to the properties of the bisphenol A skeleton, and the blocking resistance becomes good. Also, bisphenol A
The presence of the alkyl groups on both sides of the skeleton acts as a soft segment in the polymer to improve the low temperature fixability.

Among the monomers constituting the polyester in the present invention, examples of acid monomers include polyfunctional monomers having a valence of 3 or more, such as maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid and isophthalic acid. Acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, or alkenylsuccinic acid or alkylsuccinic acid such as n-dodecenylsuccinic acid, n-dodecylsuccinic acid,
Anhydrides of these acids, alkyl esters, other divalent carboxylic acids, and 1,2,4-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1 , 2,4-butanetricarboxylic acid,
1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, empor trimer Examples thereof include body acids, their anhydrides, alkyl esters, alkenyl esters, aryl esters, and other trivalent or higher carboxylic acids.

Specific examples of the alkyl, alkenyl or aryl ester described here include 1,2,4-benzenetricarboxylic acid such as trimethyl 1,2,4-benzenetricarboxylic acid and 1,2,4-benzene. Triethyl tricarboxylate, tri-n-butyl 1,2,4-benzene tricarboxylate, 1,
2,4-benzenetricarboxylate triisobutyl, 1,2,4-
Benzenetricarboxylic acid tri-n-octyl, 1,2,4-benzenetricarboxylic acid tri-2-ethylhexyl, 1,2,4-
Benzenetricarboxylic acid tribenzyl, 1,2,4-benzenetricarboxylic acid tris (4-isopropylbenzyl)
Etc.

If a large amount of tricarboxylic or higher carboxylic acid or its anhydride is used among these monomers, there is a risk of gelation during resin production if the acid value is kept below 5KOHmg / g. Requires.

Among these monomers, the following formula (I) The system in which the monomer represented by is used together shows good results.

Since the reaction of the monomer of the formula (I) proceeds by the transesterification reaction, it is possible to increase the molecular weight and to introduce a crosslinked structure regardless of the acid value of the resin (that is, even when the acid value remains low).

The mixing ratio of the monomer of the formula (I) is 2 in the constitutional unit of the acid component.
~ 50 mol% is good. If it is less than 2 mol%, a sufficient crosslinked structure cannot be obtained and the offset resistance cannot be improved.
If it is more than 50 mol%, there is a risk of gelation in resin production.

Next, the polyester used in the toner having a positive chargeability in the present invention, by its nature, needs to have an acid value of 5 KOHmg / g or less, and when it exceeds 5 KOHmg / g, the resin itself has a negative charge. It becomes more difficult and difficult to use.

Further, when the hydroxyl value exceeds 60 KOHmg / g, the molecular weight is inevitably low and the offset resistance, blocking resistance, etc. are impaired.

Next, in order to satisfy the thermal property, which is an important required property of the toner, the resin used for it has a crosslinked structure using at least one trifunctional or higher polyfunctional monomer, and the softening point of the high-performance flow tester is 90 ℃ ~ 150 ℃, it is preferable that the temperature difference between the outflow start temperature and the softening point is 15 ℃ ~ 50 ℃ (The Koka type flow tester used here is that melting behavior of resin etc. is easy at each temperature. It is a very effective device for toner and binder resin evaluation. If a polyfunctional monomer having a valence of 3 or more, that is, a cross-linking agent is not used, the offset resistance is impaired. If the softening point is less than 90 ° C, the offset resistance and blocking resistance will be impaired, and if it exceeds 150 ° C, the low-temperature fixability will be impaired. Similarly, if the temperature difference between the outflow start temperature and the softening point is less than 15 ° C, the offset resistance and blocking resistance will be impaired, and if it exceeds 50 ° C, the low temperature fixability will be impaired.

The positive charge control agent in the present invention is not particularly limited from low molecular weight compounds to high molecular weight compounds (including polymers). For example, Nigrosine-based dyes such as Nigrosine-based EX, Oil Black BS, and Oil Black S.
O ”(above, manufactured by Orient Chemical Co., Ltd.), triphenylmethane dyes, quaternary ammonium compounds, vinyl polymers having an amino group, and the like.

The content of the positive charge control agent in the electrophotographic developer composition of the present invention is preferably 0.1 to 8.0 parts by weight, more preferably 0.5 to 3.0 parts by weight, based on 100 parts by weight of the thermoplastic resin.
However, when the positive charge control agent is a vinyl polymer having an amino group, it may be used in a larger amount.

The electrophotographic developer in the present invention is produced by a usual method.

Further, as a colorant that can be used in the present invention, for example, in the case of black toner, various carbon blacks and colors produced by thermal black method, acetylene black method, channel black method, furnace black method, lamp black method, etc. In the case of toner, copper phthalocyanine, monoazo pigment (CIPigment Red 5, CIPigment
Orange 36, CIPigment Red 22), disazo pigment (C.
I.Pigment Yellow 83), Asotraquinone pigment (CIP
igment Blue 60), disazo pigment (Solvent Red 1
9), rhodamine dye (Solvent Red 49), etc.,
These are used as a colored powder, that is, a toner having an average particle diameter of 5 to 15 .mu. . As a dry two-component developer, the toner is blended with an appropriate amount of magnetic powder such as an amorphous carrier, a ferrite coated carrier, or a spherical coated carrier to be used as a developer.

Further, the magnetic fine powder can be contained in the toner for the purpose of improving the developing mechanism or the image. Examples of the magnetic powder include alloys or compounds containing elements exhibiting ferromagnetism such as ferrite and magnetite. The magnetic substance is 30 to 70 in the thermoplastic resin in the form of fine powder having an average particle size of 0.05 to 1 μm. Amounts of wt% can be used dispersed.

Known properties improvers contained in the toner according to the present invention include an anti-offset agent and a fluidizing agent.
Even if used appropriately, the present invention is not hindered at all.

The acid value and hydroxyl value of the polyester resin in the present invention are measured according to the method of JIS K 0070. However, if the resin is difficult to dissolve in the solvent, a good solvent such as dioxane may be used.

Further, the elevated flow tester used in the present invention is outlined in JIS K 7210, but in the present invention, specifically, the elevated flow tester softening temperature is as shown in FIG. Using a Koka type flow tester (manufactured by Shimadzu Corporation), 1 cm ³ of sample 3 is heated at a temperature rising rate of 6 ° C / min, and a load of 20 kg / cm ² is applied by the plunger 1 to obtain a diameter.
A nozzle 4 having a length of 1 mm and a length of 1 mm is pushed out, whereby a plunger descent amount (flow value) -temperature curve of the flow tester as shown in FIG. 2 is drawn and the height of the S-shaped curve is designated as h. At that time, the temperature corresponding to h / 2 was taken as the softening temperature, and the outflow start temperature was taken as the temperature at which the resin started to melt and the plunger started to fall.

〔Example〕

Examples of the present invention will be described below, but the present invention is not limited to these examples.

The composition ratios shown in the examples are parts by weight unless otherwise specified.

Production Example 1 (Production of Resin A) Polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane 740g Polyoxyethylene (2.2) -2,2-bis (4-hydroxyphenyl) propane 300g Terephthale Dimethyl acid 466g Isododecenyl succinic anhydride 80g 1,2,4-Benzenetricarboxylic acid tri-n-butyl 114g The above substances were put in a glass 2-liter four-necked flask together with ordinary esterification catalysts, and a thermometer and a stainless steel stirring rod were added. ,
Attach a flow-down condenser and a nitrogen inlet tube, and in an electric heating mantle heater under a nitrogen stream, the first half 210 ° C normal pressure, the second half 2
The reaction proceeded with stirring at 10 ° C. under reduced pressure.

The obtained resin has an acid value of 2.3 KOHmg / g and a hydroxyl value of 28.0 KOHmg / g.
g, Koka type flow tester had a softening temperature of 135.7 ° C and an outflow starting temperature of 102 ° C.

Production Example 2 (Production of Resin B) Polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane 1050 g Fumaric acid 298 g 1,2,4-Benzenetricarboxylic acid tri-2-ethylhexyl 156 g Methyl Hydroquinone 0.5g or more substance was used in the same manner as in Production Example 1 using the same apparatus as the first half at 185 ° C.
The reaction proceeded under normal pressure and reduced pressure at 210 ° C in the latter half.

The obtained resin has an acid value of 1.8 KOHmg / g and a hydroxyl value of 33.5 KOHmg / g.
g, Koka type flow tester had a softening temperature of 129.5 ° C and an outflow starting temperature of 98 ° C.

Production Example 3 (Production of Resin C) Polyoxypropylene (3.2) -2,2-bis (4-hydroxyphenyl) propane 1224 g terephthalic acid 398 g n-dodecyl succinic anhydride 80 g 1,2,4,5-benzenetetracarboxylic acid Tetramethyl acid 93 g or more substances were used together with a normal esterification catalyst in the same apparatus and the same process as in Production Example 1 to proceed the reaction.

The obtained resin has an acid value of 3.5 KOHmg / g and a hydroxyl value of 43.0 KOHmg / g.
g, Koka type flow tester had a softening temperature of 140.5 ° C and an outflow starting temperature of 108 ° C.

Production Example 4 (Production of Resin D) Polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane 1050g Isophthalic acid 374g 1,2,4-benzenetricarboxylic acid trimethyl 151g Glycerin 15g The reaction was carried out together with the esterification catalyst of 1. by the same apparatus and the same method as in Production Example 1.

The obtained resin has an acid value of 4.7 KOHmg / g and a hydroxyl value of 37.0 KOHmg / g.
g, Koka type flow tester had a softening temperature of 135.7 ° C and an outflow starting temperature of 100 ° C.

Production Example 5 (Production of resin E, for comparison) The same formulation except that 58 g of 1,2,4-benzenetricarboxylic acid was used instead of tri-n-butyl 1,2,3-benzenetricarboxylic acid of Production Example 1. The reaction started. The reaction proceeded while tracking the acid value, but when the acid value was close to 15 KOHmg / g, the viscosity of the resin rapidly increased and finally gelled. As a precaution, the acid value was measured and found to be 13.0 KOHmg / g.

Production Example 6 (Production of Resin F, for comparison) Polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane 1070g Isophthalic acid 97g Dimethyl terephthalate 470g The above substances were produced together with an ordinary esterification catalyst. The reaction was carried out using the same apparatus and the same method as in Example 1.

The obtained resin has an acid value of 2.7 KOHmg / g and a hydroxyl value of 20.1 KOHmg /
g, Koka type flow tester had a softening temperature of 138.8 ° C and an outflow starting temperature of 115 ° C.

Production Example 7 (Production of resin G, for comparison) Except that the tri-2-ethylhexyl 1,2,4-benzenetricarboxylic acid of Production Example 2 was changed to 55 g of 1,2,4-benzenetricarboxylic acid, the formulation was exactly the same. And proceeded with the reaction.

The obtained resin has an acid value of 19.5 KOHmg / g and a hydroxyl value of 37.2 KOHmg.
/ g, Koka type flow tester had a softening temperature of 133.2 ° C and an outflow starting temperature of 102 ° C.

Examples 1 to 4 and Comparative Examples 1 to 4 Materials having the following compositions were mixed in a ball mill, melted and kneaded in a pressure kneader, cooled, and then subjected to normal pulverization / classification steps to prepare a toner having an average particle diameter of 11 μm. .

<Composition> Example 1 Resin A 89 parts Carbon black "Carbon black # 44 (manufactured by Mitsubishi Kasei)" 6 parts Charge control agent "Nigrosine base EX (manufactured by Orient Chemical Co.)" 2 parts Wax "Viscole 550P (Sanyo Kasei Co., Ltd.)" 3) Example 2 Except that the resin A in Example 1 is changed to the resin B.

Example 3 Exactly the same as in Example 1 except that the resin A was changed to the resin C.

Example 4 Exactly the same as in Example 1 except that the resin A was changed to the resin D.

Comparative Example 1 Exactly the same as Example 1 except that the resin A was replaced with the resin F.

Comparative Example 2 Exactly the same as Example 1 except that the resin A was changed to the resin G.

Comparative Example 3 Except that the resin A in Example 1 was changed to a styrene-acrylic copolymer resin for a toner binder (crosslinking type, high-performance flow tester softening temperature 130.2 ° C.).

Comparative Example 4 Except that the resin A in Example 1 was changed to the epoxy resin "Epicoat 1007 (produced by Yuka Shell Co., Ltd.)".

The toners obtained in Examples 1 to 4 are referred to as Toner 1 to Toner 4, respectively, and the toners obtained in Comparative Examples 1 to 4 are referred to as Comparative Toner 1 to Comparative Toner 4, respectively.

39 g of each of the above toners, 1261 g of iron powder coated with a resin, and 7 g of a fluidizing agent were mixed to prepare a developer, and the triboelectric charge amount of each developer was measured by the blow-off method. And a commercially available electrophotographic copying machine (photoreceptor is an organic photoreceptor, rotation speed of fixing roller is 255 mm / sec, heat roller temperature in fixing device is variable, and oil applying device is removed)
The image was displayed at.

The fixing temperature is controlled at 120 ° C to 220 ° C, and the results of evaluating the fixing property and the offset property of the image are shown in Table 1.

What is the minimum fixing temperature here? Put a load of 500 g on a sand eraser with a bottom of 15 mm × 7.5 mm, rub 5 times over the image fixed through the fixing machine, and before and after rubbing with a Macbeth reflection densitometer. The optical reflection density is measured, and it means the temperature of the fixing roller when the fixing rate exceeds 70% as defined below.

Regarding the storage stability, the degree of aggregation was evaluated when each toner was left for 24 hours under the conditions of 50 ° C. and a relative temperature of 40%. The results are also shown in Table 1.

Regarding the resistance to migration of vinyl chloride, the image after fixing was pinched on a vinyl chloride sheet, a load of 100 g / cm ² was applied, and the state of contamination of the image and the vinyl chloride sheet was evaluated when left at 40 ° C for 1 week. . The results are also shown in Table 1.

Regarding environmental stability, high temperature and high humidity (35 ℃, 85% R
H) and image stability at low temperature and low humidity (10 ° C, 15% RH) were evaluated. The results are also shown in Table 1.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a main part of an elevation type flow tester, and FIG. 2 is a plunger drop amount (flow value) -temperature curve of the flow tester. 1 ... Plunger 2 ... Cylinder 3 ... Sample 4 ... Nozzle 5 ... Nozzle retainer

Claims (4)

[Claims] 1. An electrophotographic developer composition containing a thermoplastic resin as an essential component, wherein the thermoplastic resin has at least one polyfunctional compound having a valence of 3 or more as a constituent unit and has an acid value of 5 KOHmg / g. Hereinafter, a developer composition for electrophotography, which is a polyester having a hydroxyl value of 60 KOHmg / g or less and contains a positive charge control agent. 2. A diol component in which the thermoplastic resin is a bisphenol A alkylene oxide adduct, and the following formula (I): The electrophotographic developer composition according to claim 1, which has the compound represented by the formula (1) as an essential constituent unit. 3. The electrophotographic developer composition according to claim 2, wherein the compounding ratio of the compound represented by the formula (I) is 2 to 50 mol% in the constituent unit of the acid component. 4. The thermoplastic resin is a polyester having a softening temperature of 90 ° C. to 150 ° C. by a high-performance flow tester and a temperature difference between the outflow starting temperature and the softening temperature of 15 ° C. to 50 ° C. The electrophotographic developer composition according to item 1.